Fast neutrons will be advantageous in the treatment of cancer only if serious damage to normal tissues can be avoided and, if, compared to conventional photon treatment, fast neutrons can produce a greater effect on the tumor for an equal amount of damage to normal tissue. The aim of this investigation will be to compare the response of normal oral cavity tissues to neutrons and photons in patients receiving radiation therapy to the oral cavity in the Middle Atlantic Neutron Therapy Association (MANTA) project. MANTA, and several other centers, are currently using fast neutrons in the treatment of cancer patients. In many of these cases, part of all of the oral cavity is included within the treatment field. Both taste acuity and salivary flow and composition can be used as objective, quantitative methods of assessing normal oral cavity tissue response. The radiation response of gustatory tissue will be assessed by measuring changes in taste acuity using a forced choice-three stimulus drop technique and a forced scaling technique. The radiation response of salivary tissue will be evaluated by measuring changes in the salivary flow and amylase, zinc and total protein content of saliva collected from the parotid gland. These quantitative methods should confirm whether neutrons and photons cause equivalent normal oral tissue responses, or which treatment modality produces the greater damage. Evaluations of normal tissue response by other neutron therapy centers have failed to utilize objective, quantitative methodology as employed in this investigation.